This invention relates to a fuel injection unit and more particularly to an improved fuel injection unit that discharges both fuel and pressurized air for an engine combustion.
It is well known that the use of fuel injection can be very efficient in controlling the operation of an internal combustion engine. Fuel injection systems can provide good fuel economy and the control of unwanted exhaust gas constituents. Fuel injection systems can be particularly useful in conjunction with two cycle internal combustion engines since such engines, for their normal running, require a fairly substantial degree of overlap between the opening of the intake and scavenge ports and the closing of the exhaust port. It is obviously important to insure that the combusted mixture from the previous cycle be fully exhausted, but also it is important to insure that none of the fresh fuel/air mixture entering the engine will be discharged through the exhaust port. Fuel injection systems can be useful in insuring this result.
One well known type of fuel injection system and one which has, in fact, been used since the advent of the internal combustion engine, provides injection of both fuel and air from the injection unit. These devices work in a wide variety of manners and most generally the fuel is introduced to a chamber wherein the pressurized air resides. When the injection valve then opens, the fuel and pressurized air will both be delivered to the engine for combustion. However, this type of system has a particular disadvantage.
Specifically, it is obviously necessary to deliver the pressurized fuel to the mixing chamber at a pressure that is higher than the air pressure. When this is done, the fuel will not only enter the mixing chamber, but can flow back through the air admission system and hence when the injection valve is open, not all of the fuel may be discharged. Alternatively, the fuel discharge can be erratic from cycle to cycle as the fuel in the air system will not be discharged at regular intervals.
It is, therefore, a principal object of this invention to provide an improved fuel injection unit for an internal combustion engine.
It is a further object of this invention to provide an improved fuel injection unit for an internal combustion engine that injects both air and fuel to the engine but which will insure that the amount of fuel discharged from cycle to cycle will be uniform and the engine will run evenly under all conditions.
It is yet a further object of this invention to provide a fuel/air injection unit for an internal combustion engine wherein the fuel cannot flow into the air delivery system for the injection unit.
In order to provide the aforedescribed results, it is possible to control both the fuel and air admission by separate valves and to insure that the fuel controlling valve does not open until after the main injection has begun. Of course, this complicates the number of valves and porting arrangements that must be employed.
It is, therefore, a still further object of this invention to provide an improved fuel injection unit having a single valve arrangement that will control both the admission of the fuel and the air to the engine.